1. Field of the Invention
The invention relates to a bio-sensing device; more particularly, the invention relates to a bio-sensing device equipped with a demagnetization structure.
2. Description of Related Art
There are a number of existing cell separation technologies, such as a fluorescence activated cell separation (FACS) technology, a dielectrophoresis (DEP) cell separation technology, a micro-fabricated sieving separation technology, a magnetically activated cell separation (MACS) technology, and some optics-related and acoustics-related technologies.
Among these cell separation technologies, flow cytometry and the MACS technology are applied in most cases. Nevertheless, the frequently applied flow cytometry not only requires significant costs and a great number of samples but also has low bacterial disinfectant efficacy.
Different from flow cytometry, the MACS technology ensures that most target cells may be acquired within a relatively short period of time, and the separation principle of microbeads is based on the magnetic properties of the microbeads, i.e., the microbeads are magnetically attracted to the magnetic field and freely moved in a non-magnetic environment. Particularly, the microbeads are coated with specific antibodies which are attached to antigens of some desired cells via the antibody-antigen interaction. Thereby, the desired cells may be attached to the surfaces of the microbeads, such that the desired cells may be separated. Owing to the antibody-antigen interaction, the MACS technology is highly specific, simple, and cost-effective, and the sampling requirements for separation are low.
However, in the existing MACS technology, the microbeads with the weakened magnetic force may be gradually magnetized after being constantly controlled by the magnetic field. In the course of time, the microbeads in the wells tend to be gathered and attracted to one another even though the microbeads are not subject to any magnetic field; as a result, even in a non-magnetic environment, the microbeads can no longer move in a free manner.